In recent years, the output display of computer apparatuses are getting higher and higher in resolution. This is because a higher resolution makes it possible to display more data in one image. And, some application programs require a higher resolution than a certain level so as to display data.
In order to display such a high resolution image on a display screen, the display screen is also required to have the same high resolution. In case the resolution is raised on a display screen whose size is fixed, however, characters and patterns in display images are all shrunk according to the raised resolution, thereby the visibility of the display screen is lowered. This problem will be solved by use of a larger display screen; the resolution can be raised without shrinking the characters and patterns in the display images in this case. In the case of lap-top personal computers whose portability is very important, however, the problem still remains unsolved; because the display screen is limited physically, characters and patterns are unavoidably shrunk on the screen. In addition, even in the case of desk-top personal computers, the display screen cannot be expanded limitlessly because of their limited installation space.
In order to solve such the problem, there has been proposed a virtual screen display technique usable as means for displaying a high resolution image on a low resolution display screen. According to this technique, a display area (a view port screen) is set on a display image stored in a video memory and the data in this display area is displayed on the display screen. The view port screen is equal to the above-described display screen in size.
FIG. 11 is a chart for describing the relationship between a display image and the display area.
In FIG. 11, it is premised that the resolution of the display image 1101 is 1600 (dots)×1200 (dots) and the resolution of the display area 1102 is 800 (dots)×600 (dots). In this case, an area that is ¼ of the display image 11 in size is displayed on the display screen by taking the resolutions of both display image 1101 and display area 1102 into consideration.
According to this display technique that uses such a virtual screen, the display area 1102 can move on the display image 1101. And, when the display area 1102 moves on the display image 1101, the item displayed on the display screen is scrolled up/down and to the right/left. Generally, a GUI (Graphical User Interface) cursor (mouse pointer) is used to control the movement of such the display area 1102. Concretely, in case the mouse, while the cursor is positioned at the periphery of the display screen, is operated so as to move the cursor further to the outside of the periphery, the display area 1102 moves in the same direction in which the cursor moves.
Although it is easy to control the movement of the display area 1102 by moving the cursor as described above when a mouse, a track point, a track pad, a track ball, or the like is used, it is not so easy when a touch panel is used for controlling the movement of the display area 1102.
A touch panel is configured by a pressure-sensitive or an electrostatic panel placed on a display screen so that position information detected when a point on the display screen surface is touched is sent to a personal computer. On such a type of touch panel, when the display surface is touched by a finger of the user or an input stylus pen, the cursor is moved to the touched point.
A mouse, a track point, a track pad, a track ball, or the like uses relative pixel data so as to specify a relative point to which the cursor is to be moved from the current point. Consequently, such a device can move the cursor further to the outside of the periphery of the display screen even when the cursor is positioned at the periphery.
In case such a device is used as a pointing device, therefore, it will become easy to move the cursor to the outside of the display area 1102 on the display image 1101.
In the case of the touch panel, however, because the coordinates on the display screen correspond to the coordinates on the panel that accepts an input done by touching thereon (hereinafter, to be referred to simply as a touch input) at one to one, it is impossible to specify a point to which the cursor is to be moved outside the display area 1102. That is, because the periphery of the display screen comes to match with the periphery of the touch panel, the cursor cannot be moved to a point outside the periphery by touching it.
In order to solve this problem, a conventional technique employs a display method that uses a virtual screen and a touch panel, which is a pointing device. FIG. 9 is an illustration for describing the conventional technique. In FIG. 9, a display device 900 has areas 901 and 902. The area 901 is effective for accepting a touch input. The area 902 is an effective display area in which an image is displayed. The area 902 is equivalent to a display screen. As shown in FIG. 9, the area 901 is larger than the area 902; the area 901 spreads up to the periphery of the area 902. Concretely, this conventional technique has areas for accepting touch inputs outside the display screen.
This conventional technique accepts a touch input as an operation for specifying a movement of an item displayed on the display screen to the outside thereof on the virtual screen so as to scroll the item in case the touch input is done in the area 903 that is not overlaid on the area 902 in the area 901.
There is another conventional technique for employing the display method that uses a virtual screen and a touch panel, which is used as a pointing device. The technique is materialized as a navigation system as disclosed in Published Unexamined Patent Application No. 2000-180188. FIG. 10 is an illustration for describing the conventional technique disclosed in the specification. According to this technique, an edge portion of a display screen 1000 of the navigation system is touched so as to scroll the displayed item in the specified direction and display a range that is beyond the currently displayed map on the display screen.